The present invention relates to the field of communications. More particularly, the present invention relates to the field of Viterbi decoders utilized within a communication system.
Cellular telephony has become a widely available mode of communication in modern society. Variable rate communication systems, such as Code Division Multiple Access (CDMA) systems, are among the most commonly deployed cellular technology. Within the CDMA system, convolution encoding of data and decoding the data utilizing a Viterbi decoder are typically part of the communication process, which is well known by those of ordinary skill in the art. Furthermore, with the CDMA system there exists a traffic channel, a paging channel, and a sync channel which are all used for implementing different types of communication between a base station and a mobile station (e.g., handset). The traffic channel is utilized for transmission and reception of voice/data communication by a user. The paging channel is utilized for transmission and reception of non-user data between the base station and mobile station while the sync channel is utilized for synchronizing the base station and mobile station for communication.
As part of decoding the traffic, paging, and sync channels during communication within the CDMA system, different initialization processes of state metric data for each channel are performed depending on the type of channel being used at the time. Specifically, state metric data for both the paging channel and the sync channel are initialized using the same initialization process while state metric data of the traffic channel is initialized using a different initialization process. Typically within the prior art a circuit was specifically designed and utilized to perform the initialization process of the state metric data for the traffic channel while another circuit was specifically designed and utilized to perform the initialization process of the state metric data for both the paging channel and the sync channel. The disadvantage associated with this prior art approach is that the two circuits take up more space and add additional costs to the manufacturing process. It is appreciated that another prior approach is unable to initialize the state metric data of the traffic channel, paging channel, and the sync channel efficiently.
Accordingly, a need exists for a method and system for initializing state metric data of the traffic channel, paging channel, and sync channel within the CDMA system which does not utilize a large amount of space, does not incur higher manufacturing expenses, and also efficiently performs these initialization processes.
The present invention provides a method and system for initializing state metric data of the traffic channel, paging channel, and sync channel within a decoder within the Code Division Multiple Access (CDMA) system. Furthermore, the present invention efficiently performs these initialization processes by reducing the number of gates and hence power consumption. Moreover, the present invention does not utilize a large amount of space and also does not incur higher manufacturing expenses. Additionally, the present invention enhances performance by quickly synchronizing to paging and sync frames.
Specifically, one embodiment of the present invention includes a common circuit adapted for initializing state metric data of a traffic channel, a paging channel, and a sync channel within a Code Division Multiple Access (CDMA) system without compromising performance of any of these channels despite their different reset/initialization procedures during the encoding stage. The common circuit comprises a multiplexer stage coupled to receive a first signal and a second signal. Furthermore, the common circuit comprises a logic stage coupled to receive a plurality of signals. Additionally, the logic stage is also coupled to the multiplexer stage. As such, the multiplexer stage and the logic stage are adapted to initialize state metric data of any one of a traffic channel, a paging channel, and a sync channel within a Code Division Multiple Access (CDMA) system. It is appreciated that the common circuit does not compromise, but in fact, enhances performance of any one of the traffic channel, the paging channel, and the sync channel.
Another embodiment of the present invention also includes a method for initializing state metric data for a traffic channel, a paging channel, and a sync channel within a CDMA system without compromising performance of any channel. The method comprises the step of receiving previous state metric data. The method also includes the step of determining what channel the state metric data corresponds to within a CDMA system. Furthermore, the method includes the step of determining what stage the state metric data corresponds to. Additionally, the method includes the step of determining what state the state metric data corresponds to. Moreover, the method includes the step of initializing the state metric data based on the channel, the stage, and the state corresponding to the state metric data within the CDMA system without compromising performance of a traffic channel, a paging channel, and a sync channel.
These and other advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments which are illustrated in the drawing figures.